The temporomandibular joint (TMJ) is a synovial joint formed by the junction of the temporal bone portion of the cranium (upper section of the joint) and the superior aspect of the mandible (lower section of the joint). Between the two bones of the temporomandibular joint is an articular disc dividing the temporomandibular joint into two compartments. The upper joint compartment (formed by the articular disk and the temporal bone) is involved in translational movement (movement in a sagittal plane). The lower joint compartment (formed by the mandible and the articular disc) is involved in rotational movement (movement around a transverse oriented axis). The complex movements of the temporomandibular joint render it susceptible to various conditions and diseases affecting the function of the temporomandibular joint, referred to generally as temporomandibular joint disorders or temporomandibular joint dysfunction (TMD). Among these conditions and diseases are ankylosis, arthritis, dislocations, genetic anomalies, neoplasia and trauma.
During the evaluation of temporomandibular joint function, prosthodontists and other dental specialists use clinical experience and published research to estimate the values for a variety of temporomandibular joint positions and movements, such as:    1) anterior guidance (touching of the teeth during eccentric movements of the mandible);    2) condylar guidance (the angle at which the condyle moves away from a horizontal reference plane from centric relation along the articular eminence of the mandibular fossa);    3) immediate side shift (the lateral movement of the condyles at the commencement of mandibular laterotrusion);    4) mediotrusion/laterotrusion (thrusting of the mandibular condyle inward toward the median plane/outward away from the median plane);    5) progressive side shift (also called the Bennet angle) (the angle obtained after the non-working side condyle has moved anteriorly and medially, relative to the sagittal plane);    6) retrusion/protrusion (position posterior to the normal position/anterior to the normal position); and    7) surtrusion/detrusion (upward thrust/downward thrust).The values for these temporomandibular joint positions and movements are used to set a dental articulator to simulate motion for prosthetic design of dentures and crowns, and for masticatory assessment and masticatory research. Ideally, the values for temporomandibular joint positions and movements would be directly determined for every patient; however, disadvantageously, determining the values for temporomandibular joint positions and movements on a patient is time-consuming and expensive, and therefore is not usually done on each patient.
Therefore, there is a need for a new method for the measuring temporomandibular joint positions and movements that is not associated with the disadvantages of currently known methods.